If you are a long-term holder, what profit do you need to close the position?
For example, I need a minimum of + 400%
That's crazy high mate. I cant imagine +400% to be taken as profits because that will take very much long time. I mean that will become too much long position to be honest, and with the current bear and bull fight it can become too hard to digest. There is no way one can gain 400% in such market or not at least on the year 2018 where crypto currencies have seen worst of the bitcoin and altcoins.
For me the simple formula to win this market is, staying low! What I mean with this is simple fact, you just grab few % ranging from the 10% to 30% max which is completely doable thing and do it over and over to earn higher.
since he is a holder and wants to hold ofcourse and he is asking for a percentage rate when you are ready to sell your coin that 400% is not impossible to happen since the market of bitcoin is too low as of now ad when you look unto the past highest value of it it can really happen it can range to 300 to 400% but it will really take time.